Effects of Co-Addition of Guanidinium and Cesium to CH[sub.3]NH[sub.3]PbI[sub.3] Perovskite Solar Cells

The effects of guanidinium (C(NH[sub.2] )[sub.3] , GA) and cesium (Cs) co-additions on methylammonium lead iodide (CH[sub.3] NH[sub.3] PbI[sub.3] , MAPbI[sub.3] ) perovskite solar cells were investigated. The first-principles calculations on the density of the states and band structures showed a reduction in the total energy by the GA addition. Although the calculation showed that the co-addition of the GA/Cs to the MAPbI[sub.3] perovskite could decrease the carrier mobilities, and the addition of GA/Cs improved the device performance. This result would be due to a facilitation of grain growth and a suppression of the defects from the GA/Cs addition. The changes to the conversion efficiencies of the device with the best performance were small, which indicates that the present co-addition of GA/Cs is effective for the stability of the devices.